People often wish to cook foods, such as pizza, on their outdoor cooking grills that are not necessarily traditionally considered grill foods. For instance, with respect to pizza, the desired cooking temperature for many pizza recipes is very high, on the order of about 600 to 750° Fahrenheit. It also is important that the temperature within the cooking chamber be particularly consistent, both spatially (the temperature is substantially the same everywhere within the cooking chamber) and temporally (the temperature does not fluctuate significantly with time). First, the temperature should be spatially consistent so all of the ingredients cook properly. A common problem with cooking pizza, particularly in grills, is that the crust cooks too fast relative to the ingredients on top of the crust such that the crust becomes too dry or even burns before all of the ingredients on top of the pizza are fully cooked or properly melted. Thus, temperature uniformity as a function of height above the heating element (e.g., charcoal, wood, or flame burners) is desired. Furthermore, if the temperature is not uniform in the horizontal direction, some sections of the crust may burn before other sections of the crust are fully baked.
Even further, maintaining a consistent temperature over time also is often important to cooking pizza (as well as many other foods). First, a consistent, proper temperature will, of course, cause the food to cook faster than a fluctuating temperature and temperature fluctuations can lead to the food not cooking properly all the way through to the center.
Often, it is particularly difficult to maintain consistent temperature in cooking grills for several reasons. First, in a conventional grill, the top of the grill must be removed to place food in the grill, remove food from the grill, and observe the cooking food. Since heated air rises relative to surrounding cooler air, each time the grill cover is removed, essentially all of the heated air in the cooking chamber rises and escapes, requiring the chamber to heat up again after the cover is replaced. Not only could this cause it to take longer to cook the food, but it could lead to uneven cooking since the air in the space beneath the food is likely to remain much hotter or at least heat up much more quickly than the air in the space above the pizza after each opening of the cover. This is particularly problematic with respect to cooking pizzas because the pizza dough and/or the solid surface on which the pizza must sit (such as a pizza stone) forms a large uninterrupted barrier between the air space below the pizza and the air space above the pizza. Also, since pizza recipes often require extremely high temperatures, temperature differentials can be significant.
Kettle grills and kamado style grills are two common grill types. An exemplary kettle style grill 10 is shown in FIG. 1. An exemplary kamado style grill 20 is shown in FIG. 2. The cooking chambers 11, 21, respectively, of both of these styles of grill, respectively, (i.e., the enclosed portion containing the heating fuel and the cooking surface) are generally ovoid in shape with a circular or oval horizontal cross-section. They comprise a bottom or base portion 12, 22, respectively, and a top or cover portion 13, 23, respectively. They usually are heated by charcoal or wood placed in the bottom of the cooking chamber, although kettle and kamado grills heated by electricity or liquid fuel, such as propane, are known. Kettle style grills are often made of metal, such as steel. Kamado style grills usually are made of ceramic or other earthen materials that retain heat well. Most kettle style grills have a removable top 13, whereas kamado style grills usually have a hinged top 23 because the ceramic top is very heavy and would be difficult to handle if it were not attached. Since kettle and kamado style grills usually are round (as are pizzas) and usually are fueled by charcoal or wood so that they more easily achieve the higher cooking temperatures than electric or propane grills, they are often used for cooking pizzas.